Sample holder providing interface to semiconductor device with high density connections

ABSTRACT

A novel specimen holder for specimen support specimen support devices for insertion in electron microscopes is provided. The novel specimen holder of the invention provides mechanical support for specimen support devices and as well as electrical contacts to the specimens or specimen support devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is filed under the provisions of 35 U.S.C. §111(a) andclaims the priority of U.S. patent application Ser. No. 13/085,273 filedon Apr. 12, 2011 and U.S. Provisional Patent Application No. 61/323,107filed on 12 Apr. 2010, both of which are hereby incorporated byreference herein in their entirety.

FIELD

The invention relates generally to specimen holders used for mountingsamples in an electron microscope, e.g., a transmission electronmicroscope (TEM), a scanning transmission electron microscopy (STEM) andvariations of the scanning electron microscopes (SEM) that usetraditional TEM-type holders and stages, for imaging and analysis.

BACKGROUND

The specimen holder is a component of an electron microscope providingthe physical support for specimens under observation. Specimen holderstraditionally used for TEMs and STEMs, as well as some modern SEMs,consist of a rod that is comprised of three key regions: the end (300),the barrel (200) and the specimen tip (100) (see, e.g., FIG. 1). Inaddition to supporting the specimen, the specimen holder provides aninterface between the inside of the instrument (i.e., a vacuumenvironment) and the outside world.

To use the specimen holder, one or more samples are first placed on aspecimen support device. The specimen support device is thenmechanically fixed in place at the specimen tip, and the specimen holderis inserted into the electron microscope through a load-lock. Duringinsertion, the specimen holder is pushed into the electron microscopeuntil it stops, which results in the specimen tip of the specimen holderbeing located in the column of the microscope. At this point, the barrelof the specimen holder bridges the space between the inside of themicroscope and the outside of the load lock, and the end of the specimenholder is outside the microscope. To maintain an ultra-high vacuumenvironment inside the electron microscope, flexible o-rings aretypically found along the barrel of the specimen holder, and theseo-rings seal against the microscope when the specimen holder isinserted. The exact shape and size of the specimen holder varies withthe type and manufacturer of the electron microscope, but each holdercontains these three key regions.

The specimen holder can also be used to provide stimulus to thespecimen, and this stimulus can include temperature, electrical current,electrical voltage, mechanical strain, etc. One type of specimen holderis a semiconductor device. The semiconductor device can be designed tohave an array of electrical contact pads on it, and the sample holdercan be designed to transfer electrical signals from an external source,through the holder, to the semiconductor device. Existing devices usedelicate wires or clips to create the contact between the holder and thedevice. Further, said devices provide lower density (i.e., less)electrical contacts to the devices, which is disadvantageous when theuser wants to perform multiple experiments all on the same device.

The need for high density arrays comes from an increasing demand toperform a wider variety of experiments on a sample within themicroscope—a field known as in situ microscopy. As demonstrated inprevious filings by the present inventors, semiconductor specimensupport devices can be made to interact with the sample by passingcurrent or creating fields across or near a sample. These electricalsignals can be used to heat, cool, bias or charge a sample, all whilebeing viewed in real time within the microscope. It is an object of thepresent invention to increase the number of electrical contacts providedto a sample, thus increasing the number of or type of experiments thatcan be done on the same device.

SUMMARY

The present invention relates generally to a novel specimen holder whichprovides mechanical support for specimen support devices and as well aselectrical contacts to the specimens or specimen support devices.Specifically, a unique apparatus and method for electrically contactinga specimen support device using a small printed circuit board andelastomeric pad for conduction are described.

In one aspect, an electron microscope specimen holder is described, saidspecimen holder comprising a tip body and a clipping means.

In another aspect, a method of using a specimen holder in electronmicroscopy is described, said method comprising:

-   positioning a specimen support device in a specimen holder, wherein    said specimen holder comprises a tip body and a clipping means; and-   inserting said specimen holder in an electron microscope.

In still another aspect, a method of providing an electrical contactbetween a specimen and a specimen holder of an electron microscope isdescribed, said method comprising:

-   positioning a specimen on a specimen support device, wherein the    specimen support device comprises a frame, at least one electrical    lead and at least one membrane region; and-   inserting the specimen support device in the specimen holder,    wherein the specimen holder comprises a tip body and a clipping    means, wherein the clipping means comprise at least one electrical    contact integrated on and/or in a bottom surface of the clipping    means; and wherein at least one electrical lead of the device    substantially contacts at least one electrical contact of the    clipping means.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows a schematic of a generic specimen holder (50). The specimenholder is comprised of three regions: the tip (100), the barrel (200),and the end (300).

FIG. 2 shows a schematic of an exploded view of the various componentsof the tip of the specimen holder.

FIG. 3 shows a schematic of an exploded view of the tip of the specimenholder.

DETAILED DESCRIPTION

The present invention generally relates to novel specimen holders,methods for interfacing samples at the tip of the specimen holder, anduses of the novel specimen holder. It is to be understood that thespecimen holder and specimen holder interface described herein arecompatible with and may be interfaced with the specimen support devices,e.g., semiconductor specimen support devices, disclosed in InternationalPatent Application Nos. PCT/US08/63200 filed on May 9, 2008 andPCT/US08/88052 filed on Dec. 22, 2008, which are both incorporatedherein by reference in their entireties. It should also be appreciatedby one skilled in the art that alternative specimen support devices maybe interfaced with the specimen holder described herein. The specimenholder provides mechanical support for one or more specimens or specimensupport devices and may also provide electrical contacts to thespecimens or specimen support devices. The specimen holder can bemanufactured with tips, barrels and ends of various shapes and sizessuch that the specimen holder fits any manufacturer's electronmicroscope.

As used herein, a “specimen support device” corresponds to a structurethat holds a specimen for microscopic imaging. A specimen support devicecan provide electrical contacts and/or an experimental region. Devicesmay include one, more than one or even an array of experimental regionsand may include integrated features such as electrodes, thermocouples,and/or calibration sites, as readily determined by one skilled in theart. One preferred embodiment includes specimen support devices madewith MEMS technology and with thin membranes (continuous or perforated)for supporting a specimen in the experimental region. The specimensupport devices can provide electrical contacts or electrodes forconnection to electrical leads. The specimen support devices can alsocontain features to route electrical signals to the experimentalregion(s). The electrical signals on the specimen support devices may berouted on the specimen support device in any configuration including butnot limited to pairs of signals routed to an experimental region or arow/column addressing scheme to access a greater number of experimentalregions than the number of available signal leads. In a preferredembodiment, the specimen support device comprises a membrane comprisingat least one membrane region and at least one conductive element incontact with the membrane forming a heatable region of the membrane.

As defined herein, a “membrane region” on the specimen support devicecorresponds to unsupported material comprising, consisting of, orconsisting essentially of carbon, silicon nitride, SiC or other thinfilms generally 1 micron or less having a low tensile stress (<500 MPa),and providing a region at least partially electron transparent regionfor supporting the at least one specimen. The membrane region mayinclude holes or be hole-free. The membrane region may be comprised of asingle material or a layer of more than one material and may be eitheruniformly flat or contain regions with varying thicknesses.

As defined herein, “elastomeric” corresponds to any material that isable to resume its original shape when a deforming force is removed.Elastomers are polymeric and have a low Young's modulus and a high yieldpoint. At room temperature, elastomers tend to be soft and flexible.

The present application improves on the prior art in several ways: (1)by eliminating the required use of a delicate spring contact finger, (2)by providing a simple method for mounting and exchanging specimensupport devices and making electrical contacts to specimen supportdevices without the need for partially disassembling the specimen tip(e.g., removing screws or other small parts); and (3) by increasing thenumber of electrical contacts available thus increasing the number ofexperiments that can be performed on the specimen support device.

An exploded view of the various components of the specimen holder isshown in FIG. 2 and a detailed view of the specimen holder apparatusdescribed herein is shown in FIG. 3. The components of the specimenholder apparatus (500) include, but are not limited to, a tip body(510), an elastomeric pad (550), a printed circuit board (540), a rocker(520) and a spring pad (530).

For the purposes of the present description, a tip body (510) is amachined piece of metal that attaches to one end of the specimen holderbarrel (200). All other components listed below are attached to the tipbody. The end of the specimen holder (500) not attached to the barrel(200) contains a groove (560) and the specimen support device (see,(610) in FIG. 3) is inserted into this groove. The groove preferablyincludes guide walls or screws and a back stop.

For the purposes of the present description, an elastomeric pad (550)consists of a small rectangular piece of vacuum-compatible elastomericmaterial, such as PORON® microcellular urethane foams (RogersCorporation, Rogers, Conn.). An array of very small wires, spaced verytightly, is wrapped around the PORON material such that an unbrokenelectrical path is achieved from the top of the pad to the bottom of thepad. Metal traces on the printed circuit board (PCB) (540) electricallycontact the top of the elastomeric pad (550), while the bottom of theelastomeric pad electrically contacts the specimen support device (see(610) in FIG. 3). As such, an unbroken electrical path is formed fromthe metal traces on the PCB to the specimen support device. Theelastomeric material is somewhat soft and can slightly deform, whichallows for low force contact to the specimen support device that canaccommodate any variety of electrical contact shapes and sizes. Itshould be appreciated that the elastomeric material is not limited toPORON, as readily determined by the skilled artisan.

For the purposes of the present description, the underside of theprinted circuit board (PCB) (540) contains a row of narrow, tightlyspaced metal traces positioned over the elastomeric pad. These tracesare routed out to a series of holes in the PCB, which provide contactpoints for the wires that run from the PCB to the electrical connectoron the knob of the holder. The PCB is rigid and is physically connectedto the rocker, so the PCB can be raised and lowered by moving therocker.

For the purposes of the present description, the rocker (520) connectsthe PCB (540) and the elastomeric pad (550) to the tip body at a pinjoint pivot (570). The rocker is used to raise the PCB and elastomericpad when loading a specimen support device, and to lower the PCB andelastomeric pad when contacting a specimen support device. The top ofthe PCB (540) is attached to the bottom of the rocker (520), such thatthe elastomeric contact on the PCB extends beyond one side of therocker. A soft PORON spring pad (530) supports the other side of therocker (520). When the side of the rocker over the PORON pad is pusheddownward, the elastomeric pad on the opposite side raises, and aspecimen support device can be loaded into the groove (560). When theside of the rocker over the soft PORON pad is released, the PORON pushesthe rocker upward and the elastomeric pad on the opposite side is pusheddown onto the specimen support device, forming an electrical contact. Itshould be appreciated that other connecting means may be used to connectthe rocker to the tip body other than the pin joint pivot, as readilydetermined by the skilled artisan.

Accordingly, rather than using spring contact fingers (bent slightly attheir tips) to separately promote contact with each pad on the specimensupport device, the specimen holder described herein includes at leastmetal traces on the elastomeric pad, which bridge to corresponding metaltraces on the PCB and the specimen support device. When the specimensupport device is secured into the groove (560), the rocker providesmechanical force for securing the specimen support device in place forimaging as well as simultaneously pressing the metal traces of theelastomeric pad against corresponding metal traces on the specimensupport device.

Using the specimen holder described herein, a specimen support devicecan be mounted quickly and easily, making both physical and electricalcontacts, without the need to partially disassemble the specimen tip tomount the specimen support device.

To mount the specimen support device, downward pressure is placed on thespring pad (530) end of the rocker (520), which lifts the opposite endabove the surface to a level at least as high as the thickness of thespecimen support device, and typically higher, for example, greater than1 mm, although less than 1 mm is contemplated. The specimen supportdevice is either placed in between the clip and the mounting surfacemanually, or slid underneath the clip along the mounting surface usingthe guide screws and depth stop as guidance. Once the specimen supportdevice is in position, the rocker is released and the specimen supportdevice is secured manually to the specimen tip.

Electrical contacts from the holder to the specimen support device,typically in a range from 1 to 50 electrical contacts, are provided bythe traces on the elastomeric pad. These electrical contacts areelectrically isolated from each other. When electrical pads exist on thespecimen support device, the guide mechanism and depth stop will alignthe specimen support device with the clip to allow the electricalcontacts from the clip and the pads from the specimen support device tocontact one another when downward pressure on the clip is released. Thiswill allow both mechanical pressure and electrical connections to bemade in a novel, easy to operate design. The electrical contacts willextend from the sample holder tip to the barrel, down the barrel to theend, and to a connector that exists at the specimen holder end that canbe mated with a plug outside the microscope and connected to a powersupply to provide voltage or current through the holder and interface tothe specimen support device. Each conductor will remain isolated fromeach other as well as the three components of the specimen holder.

The advantages of the specimen holder described herein include, but arenot limited to: the ready adaptation of the specimen holder toaccommodate specimen support devices having varying shapes and sizeswithout the need to machine frames and custom parts to align differentspecimen support device geometries; providing a simple method formounting and exchanging specimen support devices and making electricalcontacts to specimen support devices without the need for partiallydisassembling the specimen tip; allowing for interchangeable specimentips to accommodate different specimen supports or to be used withdifferent barrels and ends; and eliminating the use of a delicate springcontact finger.

Although the invention has been variously disclosed herein withreference to illustrative embodiments and features, it will beappreciated that the embodiments and features described hereinabove arenot intended to limit the invention, and that other variations,modifications and other embodiments will suggest themselves to those ofordinary skill in the art, based on the disclosure herein. The inventiontherefore is to be broadly construed, as encompassing all suchvariations, modifications and alternative embodiments within the spiritand scope of the claims hereafter set forth.

What is claimed is:
 1. An electron microscope specimen holder comprisinga tip body, a soft pad, and a rocker, wherein the rocker comprises afirst end and a second end and is secured to the tip body at a pivotpoint positioned between the first end and the second end of the rocker,and wherein the soft pad is positioned between the tip body and thefirst end of the rocker such that the first end of the rocker can bedepressed to pivotally raise the second end of the rocker or the firstend of the rocker is not depressed and the soft pad pushes the first endof the rocker upward such that the second end can secure a specimensupport device between the tip body and the second end of the rockerclipping means.
 2. The specimen holder of claim 1, wherein a top surfaceof a printed circuit board is attached to a bottom surface of the secondend of the rocker.
 3. The specimen holder of claim 2, wherein a topsurface of an elastomeric pad is physically and electrically attached toa bottom surface of the printed circuit board.
 4. The specimen holder ofclaim 3, wherein a specimen support device is secured between a bottomsurface of the elastomeric pad and a top surface of the tip body.
 5. Thespecimen holder of claim 3, wherein a specimen support device is securedsuch that at least one electrical lead of the specimen support devicesubstantially contacts at least one electrical contact of theelastomeric pad.
 6. The specimen holder of claim 5, wherein an unbrokenelectrical path is formed from the printed circuit board to the specimensupport device.
 7. The specimen holder of claim 3, wherein theelastomeric pad comprises an elastomeric material and an array of wires.8. The specimen holder of claim 1, wherein the specimen holder isinserted into an electron microscope.
 9. The specimen holder of claim 1,further comprising a specimen support device mechanically securedbetween the rocker and the tip body.
 10. The specimen holder of claim 9,wherein the specimen support device comprises a frame, at least oneelectrical lead and at least one membrane region.
 11. The specimenholder of claim 9, wherein the specimen support device is aligned usinga groove.
 12. The specimen holder of claim 1, wherein the tip bodyincludes a viewing region.
 13. A method of using a specimen holder inelectron microscopy, said method comprising: positioning a specimensupport device in the specimen holder of claim 1; and inserting saidspecimen holder in an electron microscope.
 14. A method of providing anelectrical contact between a specimen and a specimen holder of anelectron microscope, said method comprising: positioning a specimen on aspecimen support device, wherein the specimen support device comprises aframe, at least one electrical lead and at least one membrane region;and inserting the specimen support device in the specimen holder,wherein the specimen holder comprises a tip body, a soft pad, and arocker, wherein the rocker comprises a first end and a second end and issecured to the tip body at a pivot point positioned between the firstend and the second end of the rocker, wherein the soft pad is positionedbetween the tip body and the first end of the rocker, wherein the rockercomprises at least one electrical contact integrated on and/or in abottom surface of the rocker; and wherein at least one electrical leadof the device substantially contacts at least one electrical contact ofthe rocker.
 15. The method of claim 14, wherein the soft pad ispositioned such that the first end of the rocker can be depressed topivotally raise the second end of the rocker or the first end of therocker is not depressed and the soft pad pushes the first end of therocker upward such that the second end can secure a specimen supportdevice between the tip body and the second end of the rocker.
 16. Themethod of claim 13, wherein a specimen is on the specimen support deviceand an electron beam is controlled to form an image of the specimen.